Reinforced Radiation-Resistant SiC-SiC Composites for Nuclear Reactors and Fuel Cladding

Advanced engineering materials are sought for use in nuclear reactors to help deploy affordable and domestic energy sources. Improved design and fabrication methods are needed to reduce cost and allow joining of nuclear-grade SiC-SiC composites for use in gas-cooled and liquid fluoride salt-cooled reactors at high temperatures. Limitations of the existing nuclear grade SiC composites as applied to high- performance nuclear systems include difficulty joining complex geometries and instability of those joints under irradiation, poor initial thermal conductivity and significant conductivity degradation after irradiation, matrix microcracking, and difficulty in producing complex shaped components at low cost. General Statement of How This Problem Is Being Addressed.The proposed SiC/SiC composite utilizes a low-cost approach incorporating a combination of SiC nanoparticles with TiC and Y2O3 to enhance joint strength, thermal conductivity, and radiation resistance. During processing, the nanoparticles are infiltrated into a SiC fiber preform, decreasing porosity and increasing conductivity. The fabrication process, consisting of a combination of nanoinfiltration and transient eutectic-phase and chemical vapor infiltration, directly addresses the requirement for low-cost manufacturing, by allowing full net shapes and the capability to be joined.What was done in Phase II?During Phase II, the best fabrication method for creating SiC composites for use in nuclear reactors was developed. These materials and methods resulted in a joined composite material with higher thermal conductivity than currently reported and high mechanical strength and bonding properties. Flat samples were joined and machined into hourglass specimens to be irradiated and tested at an outside laboratory. Simulations were conducted, and the prototype was evaluated for scalability.What is Planned for the Phase II Project?Based on research and results from Phases I and II, the fabrication method will be optimized and repeatability established. Samples will be irradiated and tested at a partner laboratory. Nuclear tie-rods or other complex shaped and joined parts selected by the project team will be created using the method developed, and tested for irradiation stability. The manufacturing methods will be refined and prototype upscaling will be considered.Commercial Applications and Other Benefits.The proposed technology will result in a high-strength, radiation- and temperature-resistant SiC composite able to be joined, and produced at low cost. It will have commercial applications in areas such as structural components and blanket structures for nuclear power plants and fuel cladding (in particular, Generation IV gas-cooled and liquid fluoride salt-cooled reactors), aerospace, and other industries. Finally, a large commercial market is envisioned in aerospace rocket and engine components, which require high-strength, high-temperature, and lightweight materials.